Abstract

Chronic intestinal inflammation is associated with pathological angiogenesis that further amplifies the inflammatory response. Vascular endothelial growth factor (VEGF), is a major angiogenic cytokine that has been implicated in chronic colitis and inflammatory bowel diseases. Endoglin (CD105), a transforming growth factor-β superfamily co-receptor expressed on endothelial and some myeloid cells, is a modulator of angiogenesis involved in wound healing and potentially in resolution of inflammation. We showed previously that Endoglin heterozygous (Eng+/−) mice subjected to dextran sodium sulfate developed severe colitis, abnormal colonic vessels and high tissue VEGF. We therefore tested in the current study if treatment with a monoclonal antibody to VEGF could ameliorate chronic colitis in Eng+/− mice. Tissue inflammation and microvessel density (MVD) were quantified on histological slides. Colonic wall thickness, microvascular hemodynamics and targeted MAdCAM-1+ inflamed vessels were assessed in vivo by ultrasound. Mediators of angiogenesis and inflammation were measured by Milliplex and ELISA assays. Colitic Eng+/− mice showed an increase in intestinal inflammation, MVD, colonic wall thickness, microvascular hemodynamics and the number of MAdCAM-1+ microvessels relative to colitic Eng+/+ mice; these parameters were all attenuated by anti-VEGF treatment. Of all factors up-regulated in the inflamed gut, granulocyte colony-stimulating factor (G-CSF) and amphiregulin were further increased in colitic Eng+/− versus Eng+/+ mice. Anti-VEGF therapy decreased tissue VEGF and inflammation-induced endoglin, IL-1β and G-CSF in colitic Eng+/− mice. Our results suggest that endoglin modulates intestinal angiogenic and inflammatory responses in colitis. Furthermore, contrast-enhanced ultrasound provides an excellent non-invasive imaging modality to monitor gut angiogenesis, inflammation and responses to anti-angiogenic treatment.